VBA code executes with message box, but not without - vba

Question

I have a Sub in VBA that I need to be able to run multiple times. When I execute this piece of code to find the last row of the sheet:
Dim lastRow As Long
With ActiveSheet
lastRow = xlWs.Cells(.Rows.count, "A").End(xlUp).Row
End With
I get
object variable or with block variable not set
when I execute it a second time, but if I add a message box before the variable set:
Dim lastRow As Long
With ActiveSheet
MsgBox xlWs.Cells(.Rows.count, "A").End(xlUp).Row
lastRow = xlWs.Cells(.Rows.count, "A").End(xlUp).Row
End With
It works no matter how many times I run it. Has anyone run into this issue before? What is wrong with the first set of code, that is corrected with the second set?

Answer 1

You are using xlWs as a worksheet object inside the block of code that you are defining lastrow and I cannot see where you have defined it prior to calling it and that is why you get an error. If by any chance you have set that object in prior code executions it and somehow that worksheet is active you will not get any error message. We just don't have more information on what the other parameters are when you are running the code or how you are running it, but the best question for you here is how to follow a clean and standard definition of objects and using them inside a good code line. I would write a function for last row and make the worksheet and column number optional:
Function LastRowInColumn(Optional sh As Worksheet, Optional colNumber As Long = 1) As Long
'Finds the last row in a particular column which has a value in it
If sh Is Nothing Then
Set sh = ActiveSheet
End If
LastRowInColumn = sh.Cells(sh.Rows.Count, colNumber).End(xlUp).row
End Function
This function will manage setting the proper sheet for you, if you enter the sheet object it will use it, if not then it will use the active sheet. The same goes for the column you want to define the last row, if you enter any column number (e.g. colNumber=3 will be column C) it will find the last row in that column, if you leave it blank, it will consider column A.

Answer 2

I have not tested this, but I've had this problem before.
I think the issue is that you are not qualifying .Rows.count. Try changing it to xlWs.Rows.count. Without it you are getting the row count of the active worksheet.
The dot operator without a preceding object points to the object defined in the With statement, even when it's inside the cells() statement, which is qualified.)
' Try This
Dim lastRow As Long
With ActiveSheet
lastRow = xlWs.Cells(xlWs.Rows.count, "A").End(xlUp).Row
End With
I'm not sure why you are using "With Active Sheet". It looks like you are trying to get the last row in worksheet xlWs, which I assume is a worksheet object.
So, the code could be simplified to this:
' Better yet, try this
Dim lastRow As Long
lastRow = xlWs.Cells(xlWs.Rows.count, "A").End(xlUp).Row
The reason the message box fixed it is because the active worksheet was changed to xlWs by doing .End(xlUp)
' This code changes the active worksheet to worksheet xlWs
' by doing .End(xlUp)
MsgBox xlWs.Cells(.Rows.count, "A").End(xlUp).Row